In the commercial software world, user interfaces are generally designed by one group. Like Microsoft for Windows or Apple for Mac OS. Those desktop environments were designed by one company who did things like user testing and statistical analysis to try and make the desktop they thought would work best. Linux is different. Large groups definitely DO perform user testing and statistical analysis, but one group can also say "Here's what we want" and, if they have the ability to code it, their idea comes into being. It's pretty amazing, when you think about it. Linux lets people create what they want. If you don't like what's out there, fork it! Or start from scratch! You're in control!

KDE it pretty close to that. I feel like I have full control over my desktop and at the same time the defaults work pretty well for everyone. I set different accounts for my friends if they ever come home and need to check anything and all of them feel comfortable with the default configuration of KDE.

And for those(like me) who need control? You can alter practically everything: you don't want taskbar? just get rid of it. You want the panel on the right monitor on the right side? Set it! You don't like maximizing on double click? change the behaviour... and that's a never ending story of things you can change